1. Field of the Invention
The present invention relates to a high power Light Emitting Diode (LED) package and a fabrication method thereof. More particularly, the invention relates to a high power LED package in which a lead part is integrated with a heat conducting member into a single component to reduce the number of components constituting the package, simplifying the assembly structure and process to reduce the manufacturing costs, and a fabrication method thereof.
2. Description of the Related Art
In general, a Light Emitting Diode (LED) is a semiconductor light emitting device that emits light in response to power applied, and adopts a PN junction diode composed of for example, GaAs or GaN optical semiconductor to convert electric energy into light.
The light from the LED ranges from red (630 nm˜700 nm) to blue-violet (400 nm), including blue, green and white. With such merits as low power consumption, high efficiency, and longer operation and life time compared with the conventional light sources such as incandescent lamps and fluorescent lamps, the demand for the LED is steadily increasing.
Recently, the LED has been expanded in its application from small-sized illumination of mobile terminals to areas such as indoor/outdoor illumination, automobile illumination, and backlights for large-sized Liquid Crystal Displays (LCD).
In the meantime, power applied to the semiconductor is increased in proportion to the intensity of light generated in response to current applied. Thus, with high level of power consumption, the LED typically adopts a heat conducting structure to prevent the semiconductor device and the package itself from being damaged from the heat generated during the emission of light.
FIG. 1(a) is a perspective view illustrating a conventional high-power LED package longitudinally sectioned, and FIG. 1(b) is a longitudinal sectional view of the conventional high-power LED package assembled onto a board.
As shown, the conventional high-power LED package 10 includes a semiconductor device 11 and a heat conducting structure 12 with the semiconductor device 11 mounted on the center of the upper surface thereof.
The semiconductor device 11 is electrically connected with a plurality of lead frames 14 via a plurality of metal wires 13 so as to be connected with external power source and applied with power.
The heat conducting structure 12 is a means to discharge the heat generated when the semiconductor device 11 emits light, thus cooling down the package. It is mounted on a board 19 via an adhesion means 12a made of material of high heat conductivity.
In the conventional LED package, the lead frame 14 is integrated with a mold part 15. The mold part 15 has an assembly hole formed therethrough so that the heat conducting structure 12 is inserted into the center of the mold part 15 to be assembled together. The lead frame 14 has one end exposed out of the mold part 15 to be connected to the wire 13, and has the other end electrically connected via a pad 14a to a circuit pattern 19a printed on the board 19.
A lens 16 is provided on the upper surface of the mold part 15 to extensively spread the light generated from the semiconductor device 11 to the outside. The space between the mold part 15 and the lens 16 is filled with packing material 17 made of transparent silicone resin to project the emitted light while protecting the semiconductor device 11 and the wires 13.
However, the conventional LED package 10 having such a structure entails forming the assembly hole 15a for inserting the heat conducting structure 12 into the center of the mold part 15, followed by the insertion of the separate heat conducting structure 12. Therefore, the assembly structure and process is too complicated to be fully automated, lowering productivity. In addition, the package has a large volume with too many components therein.
In the meantime, U.S. patent publication No. 2004/0075100 (published on Apr. 22, 2004) discloses an LED package structure including a heat conducting structure with a semiconductor device mounted thereon as a light source, a lead frame connected to the heat conducting structure and a mold part injection-molded to integrally fix the heat conducting structure with the lead frame, and a reflecting part in a cup-shape for reflecting the light generated from the semiconductor device.
In such a conventional package structure, the heat conducting member and the lead frame can be integrated with the mold part during the injection-molding of the mold part, and thus, the insertion step of the heat conducting structure can be omitted. Still, the heat conducting structure and the lead frame need to be provisionally assembled before the molding and a complicated shape of the heat conducting structure needs to be made separately. Thus, it is difficult to manage the tolerance in pre-assembly and excessively high manufacturing costs are incurred for the fabrication of the heat conducting structure. Also, flat machining is required for the component on which the semiconductor device is mounted, further increasing the manufacturing costs.